Flyback converters are widely used in the field of voltage conversion. Flyback converters can also be used in charge balancing systems which balance electrical charge between charge storage cells, like accumulator cells, in a charge storage system, like an accumulator.
A flyback converter includes input terminals for applying an input voltage, output terminals for providing an output voltage and connecting a load thereto, and a transformer with a first winding and a second winding. A switching element is connected in series with the first winding, and a rectifier element is connected in series with the second winding, wherein a first series circuit with the switching element and the first winding is connected between the input terminals, and a second series circuit with the second winding and the rectifier element is connected between the output terminals. The switching element can be switched-on and off. When the switching element is switched-on, energy is inductively stored in the transformer. This energy is transferred to the output terminals via the second winding and the rectifier element when the switching element is subsequently switched-off.
The rectifier element can be implemented as a diode, or can be implemented as a synchronous rectifier which includes a second switching element. The switching element of the synchronous rectifier is switched-on during those time periods in which the switching element connected in series with the first winding is switched-off and as long as energy is stored in the transformer. Usually, a rectifier element implemented as a synchronous rectifier has reduced losses compared with a rectifier element implemented as a diode. However, a synchronous rectifier requires an exact control of the on-times and the off-times of the second switching element in order to avoid power losses.
There is, therefore, a need for a flyback converter which has reduced power losses, and for a method for operating such flyback converter.